How about this (per Svetlin Zarev's suggestion):
binder.addCommitHandler(new CommitHandler()
{
@Override
public void preCommit(CommitEvent commitEvent) throws CommitException
{
String email = (String) commitEvent.getFieldBinder().getField("email").getValue();
EntityManager em = /* retrieve your EntityManager */;
List<?> results = em.createQuery("select idCurriculum from Curriculum where email = ?")
.setParameter(1, email)
.getResultList();
if (results.size() > 0)
throw new CommitException("Email already exists");
}
@Override
public void postCommit(CommitEvent commitEvent) throws CommitException { }
});